12.4(15)T is a pretty good guess.
Regards, Tyson Scott - CCIE #13513 R&S, Security, and SP Managing Partner / Sr. Instructor - IPexpert, Inc. Mailto: <mailto:[email protected]> [email protected] Telephone: +1.810.326.1444, ext. 208 Live Assistance, Please visit: <http://www.ipexpert.com/chat> www.ipexpert.com/chat eFax: +1.810.454.0130 IPexpert is a premier provider of Self-Study Workbooks, Video on Demand, Audio Tools, Online Hardware Rental and Classroom Training for the Cisco CCIE (R&S, Voice, Security & Service Provider) certification(s) with training locations throughout the United States, Europe, South Asia and Australia. Be sure to visit our online communities at <http://www.ipexpert.com/communities> www.ipexpert.com/communities and our public website at <http://www.ipexpert.com/> www.ipexpert.com From: [email protected] [mailto:[email protected]] On Behalf Of Bojan Zivancevic Sent: Saturday, November 27, 2010 3:17 AM To: [email protected] Subject: Re: [OSL | CCIE_RS] anybody has final verdict on OSPF external routers priority? After reading all three of your posts I can only conclude that you did not carefully read mine... The problem is that we can't be sure which IOS conforms to which RFC. I can pick one IOS and lab it up, but that would be a wild guess. I am trying to find a consistent answer. We can't be sure what IOS version of 12.4T will be on the exam. Of course, this one topic is not so big of a deal. I just like things cleared in my mind, that's all. Best Regards, Bojan Zivancevic Network Engineer ---- Comutel d.o.o. Omladinskih brigada 65v 11070 Belgrade SERBIA Tel: +381 11 217 8000 Ext.109 Mob: +381 64 646 8401 Fax: +381 11 6164641 http://www.comutel.co.rs <http://www.comutel.co.rs/> From: prakash patel [mailto:[email protected]] Sent: Friday, November 26, 2010 17:47 To: Bojan Zivancevic; [email protected] Subject: RE: [OSL | CCIE_RS] anybody has final verdict on OSPF external routers priority? Copied from cisco thread. Preference is defined as follows: (a) Intra-area and inter-area paths are always preferred over AS external paths. [OSPF] (b) Type 1 external paths are always preferred over type 2 external paths. When all paths are type 2 external paths, the paths with the smallest advertised type 2 metric are always preferred. [OSPF] (c) If the new AS external path is still indistinguishable from the current paths in N's routing table entry, and RFC1583Compatibility is set to "disabled", select the preferred paths based on the intra-AS paths to the ASBR/forwarding addresses, as specified in Section 16.4.1. Here intra-NSSA paths are equivalent to the intra-area paths of non-backbone regular OSPF areas. [NSSA] Murphy Standards Track [Page 13] RFC 3101 The OSPF Not-So-Stubby Area (NSSA) Option January 2003 (d) If the new AS external path is still indistinguishable from the current paths in N's routing table entry, select the preferred path based on a least cost comparison. Type 1 external paths are compared by looking at the sum of the distance to the ASBR/forwarding addresses and the advertised type 1 metric (X+Y). Type 2 external paths advertising equal type 2 metrics are compared by looking at the distance to the ASBR/forwarding addresses. ~[OSPF] (e) If the current LSA is functionally the same as an installed LSA (i.e., same destination, cost and non-zero forwarding address) then apply the following priorities in deciding which LSA is preferred: 1. A Type-7 LSA with the P-bit set. 2. A Type-5 LSA. 3. The LSA with the higher router ID. So your N1 with the P-bit set should take precedence over an E1 if the metrics are the same between the two! RFC 3101 by the way. _____ From: [email protected] To: [email protected] Date: Fri, 26 Nov 2010 12:35:41 +0100 Subject: [OSL | CCIE_RS] anybody has final verdict on OSPF external routers priority? I've done some research about what is the priority order in the cisco routers, regarding NSSA and regular external routes. The problem is that it seems many IOS versions are still conforming with older RFC1587, which is obsolete now because of the RFC3101. Basically, the first one says E-routes are more preffered over N-routes, if they are of the same type and with the same metric. The second one says the opposite. :) That is why labbing up such a behavior is not the answer. Does anybody know from how, say, IOS 12.4 behaves? Or 12.4T maybe? I would not like to load every single 12.4 IOS and try this out, you can imagine that. :) If someone has the answer it will save a lot of time... Best Regards, Bojan Zivancevic Network Engineer ---- Comutel d.o.o. Omladinskih brigada 65v 11070 Belgrade SERBIA Tel: +381 11 217 8000 Ext.109 Mob: +381 64 646 8401 Fax: +381 11 6164641 http://www.comutel.co.rs <http://www.comutel.co.rs/> _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
_______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
